Viscous heater for heat pump system

ABSTRACT

An air-conditioning system for a vehicle includes a heat pump system to heat the vehicle. A viscous heater is disposed within the heat pump system to supplement the heat pump system during a heat mode of the air-conditioning system.

FIELD

The present disclosure relates to a heat pump system including a viscousheater for supplementing heat during a heat mode of the heat pumpsystem.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Vehicles having internal combustion engines can use excess heat producedfrom the engine to heat a passenger cabin of the vehicle. Electricvehicles, which may not have an engine, produce little wasted heat, and,therefore, may need another heating system to heat the passenger cabin.For instance, due to their efficiency and ability to reuse componentsfrom conventional air-conditioning system, heat pumps have been utilizedin electric vehicles to heat and cool the passenger cabin.

However, heat pumps may not provide enough heating performance at verylow temperatures. To overcome such heating deficiency, the capacity of acompressor of the heat pump can be increased. Unfortunately, such anincrease may require the use of a non-standard compressor. Thus,requiring another model of a compressor which may have a lowmanufacturing output and therefore, a higher cost in piece price.Furthermore, a large compressor may not be efficient for moderateconditioning, such as mild heating, which is when the heat pump is usedmost often.

As another alternative, heat generating devices can be provided tosupplement heat to the heat pump. For instance, positive temperaturecoefficient (PTC) heaters can be used with the heat pump. However, theperformance and efficiency of the PTC heater reduces as an inlettemperature increases. The low efficiency of the PTC heater can have anegative effect on the driving range of the electric vehicle.Furthermore, PTC heaters are not typically utilized in a vehicle airconditioning system, and therefore, may be expensive to implement.

SUMMARY

This section provides a general summary of the disclosure and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure provides for an air-conditioning system for avehicle. The air-conditioning system can include a heat pump system anda viscous heater disposed within the heat pump system. The viscousheater can be configured to supplement the heat pump system during aheat mode of the air-conditioning system.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a representative vehicle including an air-conditioning systemin accordance with the present disclosure;

FIG. 2 is a schematic view of the air-conditioning system including aheat pump system as a gas injected heat pump and a viscous heater in afirst embodiment of the present disclosure;

FIG. 3 is a schematic view of the heat pump system with the viscousheater arranged between an internal condenser and the gas-liquidseparator;

FIG. 4 is a schematic view of the viscous heater coupled to a dedicatedelectric motor which powers the viscous heater;

FIG. 5 is a schematic view of the viscous heater coupled to a compressormotor which powers the viscous heater and the compressor of the heatpump system;

FIG. 6 is a schematic view of the viscous heater coupled to a fan motorwhich powers the viscous heater and a fan of the heat pump system;

FIGS. 7A, 7B, 7C, and 7D are graphs comparing the AC system of the firstembodiment with a gas injection heat pump with no supplemental heatsource (GIHP-Baseline) and a gas injection heat pump with PTC heaters(GIHP-PTC);

FIGS. 8A, 8B, 8C, and 8D are graphs comparing NVH proprieties of the ACsystem of the first embodiment, the GIHP-Baseline, and the GIHP-PTC;

FIG. 9 is a schematic view of the air-conditioning system including theheat pump system as a simple heat pump and the viscous heater in asecond embodiment of the present disclosure;

FIG. 10 is a schematic view of the heat pump system as a simple heatpump having multiple viscous heaters arranged therein; and

FIG. 11 is a schematic of the air-conditioning system including the heatpump system as the gas injection heat pump, a coolant loop, and theviscous heater in a third embodiment of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to FIGS. 1 and 2, an air-conditioning (AC) system 2 mayutilize a heat pump system 4 for heating a passenger cabin of a vehicle.The vehicle can be a hybrid or an electric vehicle, such as a plug-inhybrid electric vehicle (PHEV) or a battery electric vehicle (BEV). Thevehicle may also be a conventional vehicle having an engine, wherewasted heat from the engine may not be sufficient for heating thepassenger cabin. It would be appreciated by one skilled in the art thatthe heat pump system 4 may perform other air conditioning operations.For example, the heat pump system 4, which may include additionalcomponents, may cool the passenger cabin of a vehicle during a coolingmode of the AC system 2.

The heat pump system 4, as shown in FIG. 2, is a gas injection heat pump(GIHP) 6 that includes a compressor 8, an internal condenser 10, agas-liquid separator 12, an external heat exchanger 14, and anaccumulator 16. The AC system 2 also includes a viscous heater 18 aspart of the heat pump system 4 to assist with heating the vehicle duringthe heat mode.

The compressor 8 sucks, compresses, and discharges refrigerant into theGIHP 6. The compressor 8 can include a suction port for drawing vaporrefrigerant from the accumulator 16, a gas-injection port for receivingvapor refrigerant from the gas-liquid separator 12 via the viscousheater 18, and a discharge port for discharging compressed refrigerant.The compressor 8 may be an electric compressor that drives a fixeddisplacement compressor mechanism having a fixed charge capacity by wayof an electric motor. Various types of compressors having a fixeddisplacement compressor mechanism, such as a scroll type compressor anda vane compressor, may be employed. The compressor 8 may also be avariable displacement type compressor.

The compressor 8 is coupled to the internal condenser 10, such thatrefrigerant flows from the compressor 8 to the internal condenser 10.The internal condenser 10 can be disposed within an air duct housing ofthe AC system 2 which provides conditioned air to the passenger cabin ofthe vehicle. The internal condenser 10 heats the air flowing from anevaporator by transferring heat from the refrigerant flowing therein tothe air passing through. The air may then enter the passenger cabin ofthe vehicle via air vents provided within the passenger cabin afterbeing conditioned to a desired temperature by the AC system 2.

Refrigerant from the internal condenser 10 flows to an expansion device20 which decompresses and expands the refrigerant. From the expansiondevice 20, the refrigerant flows to the gas-liquid separator 12 whichseparates the refrigerant into its liquid and vapor forms. The liquidportion of the refrigerant can flow to the external heat exchanger 14 byway of an expansion device 21, which, like the expansion device 20,decompresses and expands the refrigerant. The vapor portion of therefrigerant flows to the compressor 8 by way of the viscous heater 18.

The external heat exchanger 14 may be disposed in a front portion of thevehicle, and exchanges heat between the refrigerant flowing therein andthe outside air being blown in by a fan. During the heat mode of theheat pump system 4, the external heat exchanger 14 performs like anevaporator by transferring heat from outside air being blown through tothe refrigerant flowing therein, thereby heating the refrigerant.

The refrigerant flows from the external heat exchanger 14 to theaccumulator 16 which separates the vapor and liquid forms of therefrigerant. The compressor 8 sucks in vaporous refrigerant from theaccumulator 16.

During the heat mode of the AC system 2, the viscous heater 18 heatsrefrigerant entering the compressor 8 of the GIHP 6. Similar to viscousheaters used in diesel engines, the viscous heater 18 generates heat byshearing viscous fluid provided within a chamber 24 of the viscousheater 18. Specifically, a rotor 26 rotates within the chamber 24 toshear the viscous fluid (FIG. 4). The heat generated is transferred torefrigerant flowing between heat exchanger fins 28 of the viscous heater18.

The viscous heater 18 can be a variable capacity heater with an ON/OFFstate function for controlling the viscous heater 18. For example, theviscous heater may be placed in an OFF state (turned off) when it is notneeded, such as during a cooling mode in which the passenger cabin ofthe vehicle is being cooled. Conversely, during the heat mode, theviscous heater 18 can be in an ON state (turned on). The viscous heater18 can be controlled by a control unit (C) 25 of the AC system 2 whichalso controls the heat pump system 4.

The control unit 25 may include a CPU, a RAM, and a ROM. The controlunit 25 receives information from various sensors disposed throughoutthe AC system 2 and from climate control gauges disposed on aninstrument panel of the vehicle which can be operated by a user. Basedon such information, the control unit 25 controls various components ofthe AC system 2 to heat and cool air to the desired temperature.

The GIHP 6 heats the passenger cabin of the vehicle by transferring heatfrom outside of the vehicle to the passenger cabin. As indicated by thearrows in FIG. 2, the compressor 8 sucks vaporous refrigerant from theaccumulator 16 and receives heated vaporous refrigerant from thegas-liquid separator 12 via the viscous heater 18. The compressor 8further compresses the refrigerant and discharges it to the internalcondenser 10.

The internal condenser 10 warms the air, which is ultimately provided tothe passenger cabin, by transferring heat from the refrigerant flowingtherein to air passing through. The refrigerant, which may now be amixture of vapor and liquid, is decompressed by the expansion device 20before being separated by the gas-liquid separator 12. From thegas-liquid separator 12, liquid refrigerant flows to the expansiondevice 21 where it can be decompressed before entering the external heatexchanger 14. By performing like an evaporator, the external heatexchanger 14 heats refrigerant flowing therein by transferring heat fromoutside air blowing through the external heat exchanger 14 to therefrigerant. Refrigerant from the external heat exchanger 14 may be amixture of vapor and liquid, and is separated by the accumulator 16.

Vaporous refrigerant from the gas-liquid separator 12 is heated by theviscous heater 18 before being injected into the compressor 8. Therefrigerant heated by the viscous heater 18 increases the temperature ofthe refrigerant discharged by the compressor 8 to the internal condenser10. Thus, the heating performance of the internal condenser and,ultimately the AC system 2, is improved.

In the event that the viscous heater 18 receives liquid refrigerant withthe vapor refrigerant from the gas-liquid separator 12, the viscousheater 18 can heat the liquid refrigerant into a vaporous form. Thus,any liquid refrigerant is prevented from entering the compressor 8.

Although the viscous heater 18 is shown in FIG. 2 as being disposedbetween the gas-liquid separator 12 and the compressor 8, the viscousheater 18 can be disposed at various suitable positions of the GIHP 6 toheat the refrigerant. For instance, as illustrated in FIG. 3, theviscous heater 18 is provided between the internal condenser 10 and theexpansion device 20, thus increasing the amount of vaporous refrigerantentering the gas-liquid separator 12. In another example, the viscousheater 18 can also be provided between the expansion device 20 and thegas-liquid separator 12.

Although only one viscous heater 18 is shown in FIGS. 2 and 3, multipleviscous heaters 18 can be utilized to supplement the heat pump system 4.For example, one viscous heater 18 can be disposed between thegas-liquid separator 12 and the compressor 8 and another can be disposedbetween the internal condenser 10 and the expansion device 20. In such aconfiguration, the refrigerant from the internal condenser 10 can beheated and decompressed before entering the gas-liquid separator 12.From the gas-liquid separator 12, the refrigerant is heated again by theother viscous heater 18 before entering the compressor 8. Thus, one ormore viscous heaters 18 can be disposed in various suitable locationsfor supplementing the heat pump system 4.

The viscous heater 18 can be powered by an electric motor using varioussuitable configurations. For instance, as illustrated in FIG. 4, adedicated electric motor 30 can be used to power the viscous heater 18.The dedicated electric motor 30 can be coupled to the rotor 26 to rotatethe rotor 26, and can be disposed with the viscous heater 18 within theheat pump system 4.

Alternatively, the viscous heater 18 can be integrated with the heatpump system 4 such that the viscous heater 18 is powered by an electricmotor already provided in the heat pump system 4. For example, asillustrated in FIG. 5, the viscous heater 18 can be powered by acompressor motor 32 which is an electric motor that powers thecompressor 8. As illustrated by the arrows, refrigerant enters theviscous heater 18 where it is heated by viscous fluid sheared by therotor 26 which is rotated by the compressor motor 32. The refrigerant isthen provided to the compressor 8 which then compresses and dischargesthe refrigerant. The viscous heater 18 can be a variable heater toprovide minimal resistance when it is not needed.

In another example shown in FIG. 6, the viscous heater 18 can also bepowered by a fan motor 34 which is an electric motor that powers a fan36. The fan 36 can be arranged near the external heat exchanger 14 toblow outside air through the external heat exchanger 14, and can be avariable output fan. To integrate the viscous heater 18 and the fan 36with the fan motor 34, one way clutches may be used to ensure properrotation of the viscous heater 18 and fan 36. The fan 36 can becontrolled so that it is not in operation when the viscous heater 18 isin operation (i.e., during the heat mode), thereby allowing the fanmotor 34 to be used for both components. Alternatively, when the fan 36and viscous heater 18 operate at the same time, a torque converter canbe used with the fan 36 to vary the torque applied to the fan 36 whenthe viscous heater 18 is in operation. For instance, the torqueconverter which may be controlled by the control unit 25, may controlthe fan 36 so that it spins slower when the fan motor 34 is rotating theviscous heater 18.

In utilizing the GIHP 6 with the viscous heater 18, the heatingperformance of the AC system 2 of the present disclosure is improvedover that of conventional methods. For instance, FIGS. 7A to 7D comparesthe heating performance of three systems during extremely cold operatingconditions: a GIHP system with no supplemental heat source(“GIHP-Baseline” hereinafter); a GIHP system having PTC heaters thatheat the air entering the internal condenser (“GIHP-PTC” hereinafter);and the AC system 2 of the present embodiment having the GIHP 6 and theviscous heater 18 (“GIHP-VH” hereinafter).

FIG. 7A provides the relative performance of the systems at extremelycold operating conditions. When the systems are at maximum performance,the GIHP-VH of the present disclosure may perform better than theGIHP-Baseline and the GIHP-PTC, as indicated by the performance bars(Qa). However, the GIHP-VH may consume more power than the other twosystems as indicated by the system load bars (L). Although the GIHP-VHconsumes more power, the overall energy consumption may be the same ormay be lower than the GIHP-Baseline and the GIHP-PTC. Specifically, theGIHP-VH may generate the same amount of heat as the GIHP-Baseline andthe GIHP-PTC in a shorter amount of time. Thus, as the vehicle warms up,the control unit 25 of the AC system 2 can switch off the viscous heater18 to maintain the efficiency of the AC system 2, thereby reducing thepower consumption of the system 2.

With reference to FIG. 7B, the coefficient of performance (COP) of thesystems is presented. Although, the GIHP-Baseline may have a higher COPthan the GIHP-VH and the GIHP-PTC, the GIHP-Baseline may not besatisfying the heating demand of the vehicle at extremely cold operatingconditions.

With reference to FIG. 7C, a percent change from the GIHP-Baseline andthe GIHP-VH is presented. The increase in performance of the GIHP-VHover the GIHP-Baseline is significantly greater than the loss in COP.The GIHP-VH also provides warmer air at an outlet of the internalcondenser than the GIHP-Baseline (shown as “% delta Air Temp” in FIG.7C).

With respect to the GIHP-PTC, the GIHP-VH has similar performance andpower consumption as the GIHP-PTC. However, as the air temperature at aninlet of the internal condenser increases, the performance of theGIHP-VH system may increase rapidly over the GIHP-PTC. Specifically, theGIHP-PTC heats the air entering the internal condenser. As an inlettemperature of the internal condenser increases, the performance andefficiency of the PTC heater decreases.

With reference to FIG. 7D, the percent change from the GIHP-PTC to theGIHP-VH is presented. The performance and the COP of the GIHP-VH areimproved over the GIHP-PTC. In addition, the GIHP-VH provides warmer airat an outlet of the internal condenser than the GIHP-PTC (shown as “%delta Air Temp” in FIG. 7D).

In addition to improved performance, the AC system 2 has improvednoise-vibration-harshness (NVH) qualities when compared to theGIHP-Baseline and GIHP-PTC. The speed of a compressor is closely relatedto the NVH qualities of the compressor. In a situation in which the sameor substantially the same level of performance is required in each ofthe system, the GIHP-VH may be the preferred system.

For instance, with reference to FIGS. 8A-8D the relative performance ofthe systems at extremely cold operating conditions is presented. TheGIHP-Baseline has about the same level of performance as the GIHP-VH andthe GIHP PTC (as indicated by bar “Qa”). However, the compressor of theGIHP-Baseline may have to operate at about 8600 rpm to achievesubstantially the same level of performance as the GIHP-VH and theGIHP-PTC, which have compressors that operate at about 3000 rpm.Accordingly, the GIHP-Baseline has a higher power consumption than theGIHP-VH and the GIHP-PTC (as indicated by bar “L”). Thus, the NVHqualities of the GIHP-VH is greatly reduced over the NVH qualities ofthe GIHP-Baseline.

With reference to FIG. 8C, a percent change from the GIHP-Baseline andthe GIHP-VH is presented. By having a compressor speed of 8600 rpm, theGIHP-Baseline has similar performance levels as the GIHP-VH (FIGS. 8Aand 8B). However, the heating performance, COP, air temperature, andcompressor speed of the GIHP-VH are an improvement over theGIHP-Baseline.

In regards to the GIHP-PTC, the GIHP-VH has about the same or similarlevel of performance as the GIHP-PTC. However, as shown in FIG. 8D, theCOP of GIHP-VH is an improvement over the GIHP-PTC at some cost toperformance. As stated above, the GIHP-VH may generate the same amountof heat as the GIHP-PTC in shorter amount of time. Therefore, once theheating requirements are met by the system, the COP may be moreimportant than heating performance.

The AC system 2 of the present disclosure may include a normal orstandard size compressor, thereby employing standard heat pumpcomponents readily available. With a standard size compressor, theGIHP-VH has improved performance capabilities over the GIHP-Baseline.The GIHP-VH may also use a smaller compressor than, for example, theGIHP-Baseline. With the smaller compressor, the GIHP-VH may have thesame performance as the GIHP-Baseline.

In utilizing the viscous heater 18 as a supplemental heat source, the ACsystem 2 may be less complex to package into the vehicle than the use ofPTC heaters. For instance, PTC heaters are typically installed in theair-duct housing which can be a standard component. Packaging spaceprovided in the air duct housing may be constrained, thereby making itdifficult to incorporate additional components like PTC heaters. Theviscous heater 18 can be integrated with heat pump components, like thecompressor 8, or installed at another position under the hood of thevehicle. Thus, the AC system 2 is able to employ standard heat pumpcomponents and achieve better heat performance by employing the viscousheater 18 with the heat pump system 4.

In the first embodiment of the present disclosure, the heat pump system4 of the AC system 2 is provided as the GIHP 6. The GIHP 6 typicallyperforms better than other heat pumps; however, the GIHP 6 can be morecomplex, costly, and can be difficult to package. As an alternative tothe GIHP 6, the heat pump system 4 can be a simple heat pump 40, asshown in FIG. 9 in a second embodiment of the present disclosure. Thesimple heat pump 40, which is less complex and less expensive, includesmost of the components of the GIHP 6 except for the gas-liquid separator12 and the expansion device 20. The simple heat pump 40 is configured toinclude the compressor 8, the internal condenser 10, the expansiondevice 21, the external heat exchanger 14, and the accumulator 16, whichall function in the same manner as in the first embodiment.

Without the gas-liquid separator 12, the compressor 8 of the simple heatpump 40 draws vapor refrigerant from the accumulator 16 via the suctionport and discharges compressed refrigerant to the internal condenser 10via the discharge port. Accordingly, the compressor 8 does not receiveadditional vaporous refrigerant which is provided in the GIHP 6 by wayof the gas-liquid separator 12. Instead, refrigerant from the internalcondenser 10, which may be in both liquid and vapor forms, flows to theexpansion device 21 and then to the external heat exchanger 14.

Similar to the first embodiment, the AC system 2 of the secondembodiment includes the viscous heater 18 which can be arranged betweencompressor 8 and the internal condenser 10. According to suchconfiguration, the simple heat pump 40 heats the passenger cabin of thevehicle by transferring heat from outside air to the passenger cabin.Specifically, as indicated by the arrows in FIG. 9, the compressor 8sucks vaporous refrigerant from the accumulator 16 and discharges it tothe viscous heater 18 which heats the refrigerant and provides it to theinternal condenser 10. As previously described, the internal condenser10 transfers heat from the refrigerant flowing therein to the airblowing through. The refrigerant, which may now include both liquid andvapor forms, flows to the external heat exchanger 14 by way of theexpansion device 21. The external heat exchanger 14 heats therefrigerant by transferring heat from outside air blowing through to therefrigerant flowing therein. From the external heat exchanger 14, therefrigerant flows to the accumulator 16 which separates the refrigerantinto its liquid and vapor forms. The compressor 8 sucks the vaporrefrigerant which is then again compressed and discharged into thesimple heat pump 40.

By arranging the viscous heater 18 between the compressor 8 and theinternal condenser 10, the viscous heater 18 heats the refrigerant fromthe compressor 8 before providing it to the internal condenser 10,thereby increasing the heating performance of the internal condenser 10and, ultimately, the AC system 2. Therefore, the simple heat pump 40having the viscous heater 18 improves the performance of the AC system 2by providing additional heat during the heat mode.

The AC system 2 of the first embodiment, which includes the GIHP 6 andthe viscous heater 18, may achieve a higher performance than the ACsystem 2 of the second embodiment, which includes the simple heat pump40 and the viscous heater 18. Based on the configuration of the ACsystem 2 of the first embodiment, the GIHP 6 has a gas injection flowpath from the gas-liquid separator 12 to the compressor 8, which, asdescribed above, is not included in the simple heat pump 40. The gasinjection flow path increases performance of the heat pump system 4 byadding high pressure, high enthalpy refrigerant to the compressor 8,thereby increasing the pressure and enthalpy of the refrigerantdischarged by the compressor 8. By heating vaporous refrigerant from thegas-liquid separator 12, the enthalpy of the vaporous refrigerantleaving the viscous heater 18 increases the effect the vaporousrefrigerant has on the compressor 8. Accordingly, the AC system 2 of thefirst embodiment, which has the GIHP 6 with the viscous heater 18, mayperform better than the AC system 2 of the second embodiment having thesimple heat pump 40 with the viscous heater 18.

Although the AC system 2 of the first embodiment may have a higherperformance than the second embodiment, the simple heat pump 40 with theviscous heater 18 can be less complex and costly than the GIHP 6 withthe viscous heater 18. In addition, the viscous heater 18 can providethe same or substantially the same level of supplemental heatperformance for the simple heat pump 40, as in the GIHP 6, when it isarranged at the same or similar position along the heat pump system 4.For instance, if the viscous heater 18 is arranged between thecompressor 8 and the internal condenser 10 for both the GIHP 6 and thesimple heat pump 40, the viscous heater 18 would have the same orsubstantially the same supplemental effect on the heat pump system 4.Therefore, by employing the simple heat pump 40 with the viscous heater18, the AC system 2 of the second embodiment provides improved heatingperformance during the heat mode with less complexity and cost.

Furthermore, the AC system 2 of the second embodiment may also employstandard heat pump components which are readily available, along withthe viscous heater 18, which can be easily integrated with the simpleheat pump 40.

Similar to the first embodiment, one or more viscous heater 18 can bedisposed at various suitable positions within the simple heat pump 40 toheat the refrigerant. For example, as shown in FIG. 10, the viscousheater 18 can be provided between the compressor 8 and the accumulator16, thereby heating vaporous refrigerant from the accumulator 16 beforeit is provided to the compressor 8. In addition, more than one viscousheater 18 can be disposed to supplement the simple heat pump 40 duringthe heat mode (FIG. 10).

Certain vehicles, such as the PHEV, may use heat from an engine or aheat pump to heat the vehicle. Such vehicles may utilize the heat pumpto heat coolant. The coolant can then be used to heat the vehicle by wayof a coolant loop. During cold temperatures, another heat source can beused to supplement the heating performance of the heat pump. Forinstance, in a third embodiment of the present disclosure, as shown inFIG. 11, the AC system 2 can be configured to have the heat pump system4 wherein the internal condenser 10 is replaced with awater-to-refrigerant heat exchanger 50. The water-to-refrigerant heatexchanger 50 is coupled to a coolant loop 52 that includes a heater core54, a pump 56, and the viscous heater 18. Although the heat pump system4 is shown as a GIHP 6, the heat pump system 4 may also be, for example,the simple heat pump 40.

The heater core 54 heats the passenger cabin of the vehicle bytransferring heat from hot coolant flowing therein to air passing thoughthe heater core 54. The coolant, which may now be cold, flows to theviscous heater 18 by way of the pump 56. The viscous heater 18 warms thecoolant before discharging it to the water-to-refrigerant heat exchanger50. The water-to-refrigerant heat exchanger 50 further warms the coolantflowing therein with the refrigerant from the heat pump system 4.Specifically, the water-to-refrigerant heat exchanger 50 transfers heatfrom the refrigerant to the coolant which then flows to the heater core54. The refrigerant leaving the water-to-refrigerant heat exchanger 50is heated by the heat pump system 4.

Although the viscous heater 18 is provided within the coolant loop 52 inFIG. 11, the viscous heater 18 can be provided within the heat pumpsystem 4. For instance, the viscous heater 18 can be disposed betweenthe gas-liquid separator 12 and the compressor 8, thereby allowing theviscous heater 18 to supplement the AC system which has a coolant loop.Furthermore, in addition to the viscous heater 18 provided within thecoolant loop 52, another viscous heater can be disposed between withinthe heat pump system 4. For example, another viscous heater can bedisposed between the gas-liquid separator 12 and the compressor 8.

By having the viscous heater 18 disposed before the water-to-refrigerantheat exchanger 50, the viscous heater 18 preheats the coolant going intothe water-to-refrigerant heat exchanger 50. Accordingly, the refrigerantleaving the water-to-refrigerant heat exchanger 50 may have a highertemperature than the refrigerant leaving the water-to-refrigerant heatexchanger 50 when the viscous heater 18 is not provided to preheat thecoolant. As a result, the external heat exchanger 14, which can limitthe performance of the AC system 2, receives warmer refrigerant at ahigher flow rate, thereby increasing the performance of the heat pumpsystem 4.

Furthermore, the third embodiment may provide for a more flexible designthan the first and second embodiments. For instance, if conventionalhybrid and electric vehicles have the same heat pump system 4, the heatpump system 4 can still be supplemented by disposing the viscous heater18 along the coolant loop 52 instead of the heat pump system 4.

Although the use of the viscous heater 18 with the heat pump system 4 isdescribed in relation to the AC system 2 of the vehicle, it should beunderstood that the viscous heater 18 and the heat pump system 4 can beused in other thermal control operations. For example, the viscousheater 18 can be used with the heat pump system 4 and/or coolant loop 52to control the temperature of a battery pack used in hybrid vehicles andelectric vehicles.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

What is claimed is:
 1. An air-conditioning system for a vehiclecomprising: a heat pump system conditioning air for a passenger cabin ofa vehicle; and a viscous heater disposed within the heat pump system,wherein the viscous heater receives and heats refrigerant flowing in theheat pump system.
 2. The air-conditioning system of claim 1, wherein aplurality of the viscous heaters are disposed within the heat pumpsystem.
 3. The air-conditioning system of claim 1, wherein the viscousheater includes an electric motor.
 4. The air-conditioning system ofclaim 1 further comprising: a coolant loop coupled to the heat pumpsystem for conditioning the air for the passenger cabin of the vehicle.5. The air-conditioning system of claim 4 further comprising: anotherviscous heater disposed along the coolant loop for heating coolantflowing in the coolant loop.
 6. An air-conditioning system for a vehiclecomprising: a heat pump system including a compressor compressingrefrigerant flowing therein, an internal condenser communicating withthe compressor for receiving the refrigerant and exchanging heat betweenthe refrigerant flowing therein and air blowing through the internalcondenser, an external heat exchanger communicating with the internalcondenser for receiving the refrigerant and exchanging heat between therefrigerant flowing therein and air blowing through the external heatexchanger, and an accumulator communicating with the external heatexchanger for receiving the refrigerant and communicating with thecompressor for providing the refrigerant; and a viscous heater disposedwithin the heat pump system, the viscous heater receiving and heatingthe refrigerant flowing in the heat pump system.
 7. The air-conditioningsystem of claim 6 wherein the heat pump system further comprises anelectric motor that powers the compressor and the viscous heater.
 8. Theair-conditioning system of claim 6, wherein a plurality of the viscousheaters are disposed within the heat pump system.
 9. The airconditioning system of claim 6 wherein the heat pump system furthercomprises: a fan that blows air through the external heat exchanger; andan electric motor that powers the fan and the viscous heater.
 10. Theair-conditioning system of claim 6, wherein the heat pump system furtherincludes: a gas-liquid separator that communicates with the internalcondenser to receive the refrigerant, the gas liquid separator separatesthe refrigerant into vapor and liquid forms, and the gas-liquidseparator further communicates with the compressor and the external heatexchanger to substantially provide the vapor form of the refrigerant tothe compressor and the liquid form of the refrigerant to the externalheat exchanger.
 11. The air-conditioning system of claim 10, wherein theviscous heater is disposed between the compressor and the gas-liquidseparator, the viscous heater communicates with the gas-liquid separatorto receive the vapor form of the refrigerant and communicates with thecompressor to provide the vapor form of the refrigerant after heatingthe refrigerant received from the gas-liquid separator.
 12. Theair-conditioning system of claim 6, wherein the viscous heater includesan electric motor.
 13. An air-conditioning system for heating andcooling a vehicle comprising: a heat pump system including a compressorcompressing refrigerant flowing therein, a water-to-refrigerant heatexchanger communicating with the compressor for receiving therefrigerant and exchanging heat between the refrigerant and coolant, anexternal heat exchanger communicating with the water-to-refrigerant heatexchanger for receiving the refrigerant and exchanging heat between therefrigerant flowing therein and air blowing through the external heatexchanger, and an accumulator communicating with the external heatexchanger for receiving the refrigerant and communicating with thecompressor for providing the refrigerant; a coolant loop communicatingwith the water-to-refrigerant heat exchanger of the heat pump system forproviding the coolant; and a viscous heater providing supplemental heat.14. The air-conditioning system of claim 13, wherein the viscous heateris disposed within the heat pump system to heat the refrigerant flowingin the heat pump system.
 15. The air-conditioning system of claim 13wherein the viscous heater is disposed within the coolant loop to heatthe coolant flowing in the coolant loop.
 16. The air-conditioning systemof claim 15, further comprising: at least one other viscous heaterdisposed within the heat pump system for receiving and heating therefrigerant flowing in the heat pump system.
 17. The air-conditioningsystem of claim 13, wherein the viscous heater further comprises anelectric motor.
 18. The air-conditioning system of claim 13, wherein thecoolant loop includes a heater core that exchanges heat between thecoolant flowing therein and air blowing through the heater core, and apump that communicates with the heater core for pushing the coolantthrough the coolant loop, and the viscous heater is disposed between thepump of the coolant loop and the water-to-refrigerant heat exchanger ofthe heat pump system, the viscous heater communicates with the pump toreceive the coolant and communicates with the water-to-refrigerant heatexchanger to provide the coolant after heating the coolant received fromthe pump.